One of the progressively more urgent environmental problems of modern times is posed by increasing air pollution, to which noxious substances produced by a wide variety of combustion processes are making a not insubstantial contribution.
The list of such products of combustion is headed in particular by gasses having a harmful impact on the climate such as nitrogen oxides and carbon dioxide.
The environment is also polluted with the above-mentioned climatically harmful gasses produced from generating electrical energy by the burning of fossil fuel.
In the case of a gas-fired power station, for instance, these gasses are contained in the exhaust gas of a gas turbine and have to be suitably handled in particular for the purpose of complying with the prescribed emission standards.
This problem is somewhat less pronounced in the case of power stations employing a combined gas/steam process because, owing to their high degree of efficiency compared to pure gas-fired or pure steam-powered power stations, power stations of this type operated by means of both gas and steam produce fewer gasses that are harmful to the climate.
However, even these power stations require substantial effort to handle the climatically harmful gases they produce in an environmentally friendly manner.
Precipitation of the carbon dioxide produced during the combustion of hydrocarbons, such as natural gas or heating oil, or of synthetic gasses, such as gasses resulting from a gasification of coal, heavy oil or biomass, can occur as a result, for example, of intense cooling of the combustion gasses to substantially below 0° C., during which initially water forms followed by carbon dioxide in liquid form, with the possibility that the latter may freeze if cooling is very intense and thus appear in solid form.
This liquid or solid carbon dioxide can then be stored so that it can no longer escape into the atmosphere and mix with air.
However, typical exhaust gas of a gas turbine contains approximately only 5-10% carbon dioxide and more than 70% nitrogen and/or nitrogen compounds, so that a very substantial amount of exhaust gas has to be cooled in order to precipitate the relatively small amount of carbon dioxide. This necessities correspondingly large dimensioning of a carbon dioxide precipitation plant provided for this purpose and is associated with high energy requirements.